There is a need for ships which can provide a seabasing capability; combining roles of transporting or housing aircraft, vehicles, and personnel. In existing naval fleets, these roles are usually separated, and ships that fulfill one or more of these roles are often of limited capacity and capability. Furthermore, prior art proposals for seabasing ships have been either very slow or had a very limited capacity for large transport aircraft.
Fixed-wing tactical aircraft operating from large aircraft carriers have been a key component of major surface navies for the last 65 years. Among the most prominent examples are the US Navy's nuclear aircraft carriers, CVN, as shown in FIG. 1. The flight deck 102 is constructed on top of a ship hull 104 and features catapults 106 aligned with the ship to facilitate aircraft launch, and arresting wires oriented across a landing area 108 of the flight deck for aircraft recovery
Amphibious assault ships (such as the US Navy LHA and LHD, FIG. 2) provide marine units a seaborne platform for support of combat operations from the sea. Vertical takeoff aircraft 202 are positioned on the flight deck 204 of a LHD ship 200, takeoff marks 206 aligned with the ship indicate from where aircraft can launch. While such ships rely primarily on air-cushion landing craft to deploy heavy combat-ready vehicles, including armored vehicles, to a beachhead, they also provide facilities for helicopter transport of troops, light vehicles, and supplies.
The US military uses special roll-on roll-off (RO-RO) ships (FIG. 3) to pre-position heavy armored vehicles close to where they may be needed. Such a ship 300 includes provisions 302 for armored vehicles to drive onboard, and typically minimal helicopter landing provisions 304. The deployment of heavy legacy armor including Abrams battle tanks and Bradley armored troop carriers, heavy artillery, and engineer vehicles requires substantial port facilities in the area of operation to deploy on land.
Recently, the US Army has invested in the development of lighter-weight survivable armored vehicles, with program names of Interim Brigade and Future Combat System. This revamped Army plan would provide highly mobile units with vertical maneuver capabilities using a proposed Joint Heavy Lift aircraft to transport light armored vehicles, crews, and combat troops into battle and back at typical radii of deployment of 250 to 750 nautical miles. As used herein, Joint Heavy Lift (JHL) aircraft shall refer to aircraft and aircraft concepts capable of transporting armor or troops and capable of vertical takeoff. Especially preferred JHL aircraft include tilt-rotors with two rotors of 65, 75, 80, or even 90-foot diameter each and are capable of carrying payloads of 20,000, 40,000, 60,000, 80,000, or even 100,000 pounds.
Due to the possible lack of land bases near future battlefields, vehicles, troops, and JHL aircraft may be supported and deployed from large ships or mobile basing platforms, under the concept generally referred to as seabasing. Many prior art alternatives for providing a seabasing capability have been studied, and generally these fall into two principal categories.
The first category comprises very large structures based on oil platform technology, such as the prior art mobile offshore base (MOB, FIG. 4), sized for conventional takeoff of aircraft (up to 5,000 feet long and 500 feet wide). A MOB 400 has a runway 402 dimensioned for the requirements of conventional takeoff transport aircraft 404. The MOB concepts proposed have typically comprised three to five joinable sections, each section being transported separately, usually with the aid of tugboats. While the MOB Seabasing platform can carry and operate many aircraft, it is an almost stationary platform when assembled on station, with maximum speeds of approximately 5 knots, and a very high cost, estimated to be $8-10 billion in 2007.
The second category of prior art is based on adaptations of large ships of various types, including commercial containerships, a prior art example is shown in FIG. 5. A converted containership 500 has a hull 502 and is equipped with a flight deck 504 and aircraft 506 can launch or recover from takeoff and landing spots 508 aligned with the ship. The aircraft 506 pictured is a small Bell™ V-22 tilt-rotor having 38 foot diameter rotors. It is estimated that the ship 500 would have a capacity of only 4 to 5 large JHL aircraft having 75 foot diameter rotors. Prior art containership conversions have also left the original containership superstructure 510 largely intact, which prevents the on-deck transport of large aircraft between the bow and aft ends of the flight deck. While a short sponson 512 enlarges the breadth of the flight deck somewhat beyond that of the original containership beam, the enlarged portion extends for a length of only about 15-20% of the flight deck length.
Some other purpose-built concepts have also been proposed, as exemplified in FIG. 6, which is a seabasing ship 600 that is similar to a floating platform but is designed for faster travel, but still slow with a sustained speed of no more than 5-10 knots. This proposed ship 600 has a length of approximately 1180 feet, an overall breadth of about 650 feet, and an operating displacement of about 588,000 short tons. Unless the context dictates the contrary, all ranges set forth herein should be interpreted as being inclusive of their endpoints.
The present inventive material focuses on seabasing ships derived from container ships that offer sufficient speed (23-25 knots) to operate in company with existing ships (CVN aircraft carriers, destroyers, and cruisers). However, all previously proposed seabasing conversion concepts are arranged to carry very few JHL-scale aircraft, a limitation which prevents a high rate of aircraft sortie generation, which is vital for the combat deployment of armored or mechanized forces. Furthermore, previously proposed seabasing conversion concepts have featured flight decks which were only as wide as the containership beam. To increase the rate of aircraft sortie generation, it is further advantageous to have a large number of aircraft simultaneously ready for take-off.
As used herein, the term “ready for take-off” means that the aircraft can be launched into the air without substantially re-orienting, re-spotting, or re-configuring the aircraft. Examples of aircraft being ready for take-off include a jet on the catapult on an aircraft carrier, or a JHL aircraft or helicopter that is positioned at a takeoff position on a helicopter launching pad or on a flight deck. In FIG. 1, for example, none of the aircraft are “ready for takeoff” as defined herein because every one of them must be re-oriented or re-spotted onto a catapult. In FIG. 2, none of the aircraft are “ready for takeoff” as defined herein because in every one of them must be re-oriented or re-spotted to a takeoff spot with adequate clearance. The mobile offshore base of FIG. 4 has one aircraft 406 ready for takeoff on a conventional runway. FIG. 5 shows three tilt-rotors ready for takeoff, but they are all have orientation angles of zero consistent with other prior art. FIG. 6 shows multiple rotorcraft ready for takeoff, but the ship is really a modified oil platform, which is not configured to realistically exceed 15 knots.
The major reason for the limited number of JHL aircraft accommodated on the flight deck of currently proposed and prior art fast ships is the general assumption that aircraft must align into the wind, or most commonly toward the ship's bow, for launch and recovery operations. To the best knowledge of the Applicant, this is consistent with standard naval operating procedure. Conventional aircraft positioning also requires military vehicles, while being loaded into their assigned aircraft, to maneuver between the aircraft being loaded and the one directly behind it. This results in further required separation between aircraft and reduces the tempo of vehicle loading, to avoid an increased risk of damage to aircraft due to accidental contact.
The issue of the number of JHL aircraft on a fast seabasing ship becomes more critical in view of the currently preferred aircraft configuration for a fast, long-range and efficient JHL, a large wing-span tilt-rotor aircraft with two rotors of 75 foot diameter each.
Therefore, there remains a need for a fast ship (23-27 knots), with affordable cost ($500 million or less when fully equipped for military seabasing), which can carry and operate a large number of JHL aircraft of the preferred configuration, and facilitate a high rate of aircraft recovery, loading, and launch.